Dysregulated cholinergic signaling inhibits oligodendrocyte maturation following demyelination

Abstract

Dysregulation of oligodendrocyte progenitor cell (OPC) recruitment and oligodendrocyte differentiation contribute to failure of remyelination in human demyelinating diseases such as multiple sclerosis (MS). Deletion of muscarinic receptor enhances OPC differentiation and remyelination. However, the role of ligand-dependent signaling versus constitutive receptor activation is unknown. We hypothesized that dysregulated acetylcholine (ACh) release upon demyelination contributes to ligand mediated activation hindering myelin repair. Following chronic cuprizone induced demyelination (male and female mice), we observed a 2.5-fold increase in ACh concentration. This increase in ACh concentration could be attributed to increased ACh synthesis or decreased acetylcholinesterase (AChE) / butyrylcholinesterase (BChE) mediated degradation. Using ChAT reporter mice, we identified increased ChAT-GFP expression following both lysolecithin and cuprizone demyelination. ChAT-GFP expression was upregulated in a subset of injured and uninjured axons following intraspinal lysolecithin induced demyelination. In cuprizone demyelinated corpus callosum, ChAT-GFP was observed in Gfap⁺ astrocytes and axons indicating the potential for neuronal and astrocytic ACh release. BChE expression was significantly decreased in the corpus callosum following cuprizone demyelination. This decrease was due to the loss of myelinating oligodendrocytes which were the primary source of BChE. To determine the role of ligand mediated muscarinic signaling following lysolecithin injection, we administered neostigmine, a cholinesterase inhibitor, to artificially raise ACh. We identified a dose-dependent decrease in mature oligodendrocyte density with no effect on OPC recruitment. Together, these results support a functional role of ligand mediated activation of muscarinic receptors following demyelination and suggest that dysregulation of ACh homeostasis directly contributes to failure of remyelination in MS.Significance Statement Demyelinating diseases like Multiple Sclerosis are characterized by failure of remyelination. Oligodendrocyte progenitor cell (OPC) recruitment and differentiation are crucial aspects for remyelination to occur. Here we show that increased acetylcholine (ACh) contributes to activation of muscarinic receptors that inhibit OPC differentiation. Increased choline acetyltransferase synthesis following demyelination was observed in axons and astrocytes suggestive of a potential for acetylcholine synthesis and release. The increase in ACh levels following demyelination was largely due to reduction of oligodendrocyte derived butyrylcholinesterase that modulates ACh concentration. Development of cell specific esterase stimulator to restore ACh levels may serve as an approach towards inhibiting ongoing demyelination and neurodegeneration.